The present disclosure relates to a touch panel apparatus which is suitably applicable to a projection electrostatic-capacitance touch-panel apparatus and a touch-panel detection method.
An electrostatic-capacitance touch panel employing a projection method has been in practical use and has been used in various electronic apparatuses. In a projection electrostatic-capacitance touch-panel in which transparent electrodes are arranged in a grid pattern as two layer structures on a transparent substrate on a display panel such as a liquid crystal display panel, a touch position is detected by detecting change of electrostatic capacitance caused by a finger touch. Note that, in the electrostatic-capacitance touch panel, in addition to a case where a panel surface is directly touched by a finger, a case where a finger approaches the panel surface may be detected by change of the electrostatic capacitance.
Since the electrostatic-capacitance touch panel detects change of electrostatic capacitance, in a waiting state for detection of a touch, a signal is continuously applied to the electrodes of the touch panel so that touch detection may be performed.
FIGS. 15A and 15B show examples of general driving of the electrostatic-capacitance touch panel.
In general, in the electrostatic touch panel, two states, i.e., an active state in which touch detection is being performed and an idling state in which the panel is in a standby state until a touch is detected are set.
FIG. 15A shows a driving example in the active state and FIG. 15B shows a driving example in the idling state. In FIGS. 15A and 15B, axes of ordinate denote power consumption of a driving signal and axes of abscissa denote time.
The driving example in the active state shown in FIG. 15A will be described. When the panel surface is touched by a finger, for example, the touch state should be detected in a comparatively short cycle, and therefore, a waiting time after a measurement is set to be short so that a comparatively short measurement cycle is attained. One measurement cycle is approximately 20 to 50 ms, for example. Since the measurement cycle is set to be short, excellent touch detection may be performed in accordance with movement of the finger.
The driving example in the idling state shown in FIG. 15B will be described. In a state in which the finger or the like is not touched to the touch panel, for example, the waiting time after a measurement is set to be long so that a measurement cycle is set to be long. Accordingly, power consumption of the touch panel is reduced. One measurement cycle is approximately 50 to 100 ms, for example.
When the touch state is detected in the idling state, the active state is entered. When a touch is not detected for a predetermined period of time in the active state, the idling state is entered.
Japanese Unexamined Patent Application Publication No. 2010-72743 discloses a configuration of an electrostatic-capacitance touch panel and a detection principle.